Sintering a Multi-lobed Helical Rotor

ABSTRACT

The present disclosure relates to a method and system for manufacturing a multi-lobed helical rotor. The method for manufacturing a multi-lobed helical rotor may comprise mixing one or more powdered metals, compacting a mixture of one or more powdered metals to form a solid metal piece, sintering the solid metal piece, and polishing the solid metal piece. The system may comprise a positive displacement pump, which may comprise a casing, a multi-lobed helical rotor disposed in the casing, wherein the multi-lobed helical rotor comprise sintered powdered metals, an inlet to the casing, and an outlet leading from the casing.

BACKGROUND

The present disclosure relates to a method and process for manufacturingparts and tools used in the oilfield. More particularly, the presentdisclosure relates to the manufacturing of multi-lobed helical rotorswith sintered powdered metals.

Various types of parts and tools are currently used in the oilfield.Current methods of manufacturing rotors may take forty or more hours toproduce a finished product. Milling a multi-lobed helical rotor mayrequire removal of large amounts of material from a metal block. Thisgenerates large amounts of waste material and significant consumption ofmilling bits and tools. Additionally, after the milling process, amilled multi-lobed helical rotor and/or other oilfield tools may needpolishing, grinding, and/or additional finishing steps. Polishing maytake as much as fifteen hours to complete and may require the use ofsanding disks and/or belts. This makes the current manufacturing processof oilfield parts and tools expensive, wasteful, and time intensive.

BRIEF DESCRIPTION OF THE DRAWINGS

These drawings illustrate certain aspects of some of the examples of thepresent invention, and should not be used to limit or define theinvention.

FIG. 1 is an illustration of an example of a multi-lobed helical rotorwithin a pump;

FIG. 2 is a schematic illustration of an example multi-lobed helicalrotor manufacturing process;

FIG. 3 is an illustration of an example of multi-lobed helical rotordie; and

FIG. 4 is an illustration of an example of a drilling system using apositive displacement pump.

DETAILED DESCRIPTION

The present disclosure relates generally to a method and process formanufacturing parts and tools used in the oilfield. More particularly, amethod and process for manufacturing a multi-lobed helical rotor. Thedisclosure describes a method and process that manufactures parts andtools used in the oilfield through sintering powdered metal.Specifically, a process may comprise mixing powdered metals, compactingthe powdered metals, sintering the powdered metals, and polishing theresultant product. Many oilfield tools and parts are speciallymanufactured to meet stringent requirements for oilfield use. Sinteringpowdered metals may drastically cut the time it takes to produceoilfield tools and parts while retaining stringent specifications.

Certain examples of the present disclosure may be implemented at leastin part with an information handling system. For purposes of thisdisclosure, an information handling system may include anyinstrumentality or aggregate of instrumentalities operable to compute,classify, process, transmit, receive, retrieve, originate, switch,store, display, manifest, detect, record, reproduce, handle, or utilizeany form of information, intelligence, or data for business, scientific,control, or other purposes. For example, an information handling systemmay be a personal computer, a network storage device, or any othersuitable device and may vary in size, shape, performance, functionality,and price. The information handling system may include random accessmemory (RAM), one or more processing resources such as a centralprocessing unit (CPU) or hardware or software control logic, ROM, and/orother types of nonvolatile memory. Additional components of theinformation handling system may include one or more disk drives, one ormore network ports for communication with external devices as well asvarious input and output (1/0) devices, such as a keyboard, a mouse, anda video display. The information handling system may also include one ormore buses operable to transmit communications between the varioushardware components.

An example of a method for manufacturing a multi-lobed helical rotor maycomprise mixing one or more powdered metals, compacting a mixture of theone or more powdered metals to form a solid metal piece, sintering thesolid metal piece, and polishing the solid metal piece. The method mayfurther comprise choosing one or more powdered metals as the basematerial for the multi-lobed helical rotor. The method may comprisechoosing the one or more powdered metals and at least one additive asthe base material for the multi-lobed helical rotor. The step of mixingmay comprise combining the one or more powdered metals with at least oneadditive and the step of compacting may comprise adding the at least onepowdered metal and at least one additive to a die. The step ofcompacting may comprise compacting at least one powdered metal and atleast one additive with a hydraulic ram. The step of compacting at leastone powdered metal and at least one additive with a hydraulic ram mayform the multi-lobed helical rotor. The step of sintering may compriseplacing the multi-lobed helical rotor in a furnace, wherein the furnacemay be a multi-belt furnace. The step of polishing may be performed byan abrasive flow machine. The step of compacting and the step ofsintering may be combined into a single step in which the compacting maybe performed at elevated temperatures.

A system may comprise a positive displacement pump which may furthercomprise a casing, a multi-lobed helical rotor disposed in the casing,wherein the multi-lobed helical rotor may comprise sintered powderedmetals, an inlet to the casing, and an outlet leading from the casing.The sintered powdered metals may be formed from powdered metals having aparticle size of about 0.5 microns to about 100 microns. The multi-lobedhelical rotor may comprise 17-4 stainless steel, wherein the multi-lobedhelical rotor may further comprise at least one additive selected from agroup which may consist of plastic, carbon, copper, wax, and/orcombinations thereof. The system may further comprise a secondmulti-lobed helical rotor disposed in the casing, wherein the secondmulti-lobed helical rotor may comprise sintered powdered metal. Thesystem may further comprise feed conduit coupled to the positivedisplacement pump, and a drill string coupled to the feed conduit,wherein the drill string may be at least partially disposed in awellbore. The system may further comprise a derrick comprising atraveling block for raising and lowering the drill string, wherein thepositive displacement pump may be connected to a solids control system.The solids control system may be connected to a retention pit.

FIG. 1 illustrates an example of a positive displacement pump 2.Positive displacement pump 2 may comprise a multi-lobed helical rotor 4,a casing 6, an inlet 8, and an outlet 10. It should be noted thatpositive displacement pump 2 may comprise more than a single and/or aplurality of multi-lobed helical rotors 4. In examples, a positivedisplacement pump may produce the same flow at any given speed, nomatter what the discharge pressure may be. Positive displacement pumpsmay be considered constant flow machines. Benefits of using positivedisplacement pumps, for example a lobe pump, within the chemicalindustry may be the sanitary qualities, high efficiency, reliability,corrosion resistance, and good clean-in-place and steam-in-placecharacteristics. Additionally, positive displacement pumps may be ableto handle solids, slurries, pastes, and a variety of liquids.

The manufacturing process of a multi-lobed helical rotor 4, and anassociated method, may embody principles of this disclosure. However, itshould be clearly understood that the process and method ofmanufacturing a multi-lobed helical rotor 4 may be one example of anapplication of the principles of this disclosure in practice. A widevariety of manufactured oilfield tools and parts may be possible withthe disclosed process and methods. Therefore, the application of thisdisclosure is not limited to the details of a manufacturing process fora multi-lobed helical rotor 4 and method as described herein and/orillustrated in the drawings.

As illustrated in FIG. 1, a multi-lobed helical rotor 4 may comprise aplurality of lobes 12. Multi-lobed helical rotor 4 and lobes 12 may bemade of any suitable material to withstand the pressures and chemicalsthat they may contact. This may make the material makeup of multi-lobedhelical rotor 4 an important factor during manufacturing. Additionally,individual lobes 12 may be of any suitable diameter, shape, angle, twistrate, and/or orientation to satisfy pumping requirements. Manufacturinga multi-lobed helical rotor 4 and lobes 12 may be complex, requireprecision, and be time intensive. In some known methods, millingmachines may be used to produce multi-lobed helical rotors 4. Millingtimes may take forty hours before completion and may require anadditional fifteen hours of polishing before a multi-lobed helical rotor4 may be ready for service. The high demand for these complex parts maymake the forty to fifty-five hour manufacturing time an inefficient andcostly process.

FIG. 2 illustrates a manufacturing process that may be used to cut theproduction time of multi-lobed helical rotor 4. The process may usepowdered metals and a sintering process to manufacture multi-lobedhelical rotor 4. The process may comprise mixing 14 powdered metals,compaction 16 of the powdered metals, sintering 18 the powdered metals,and polishing 20 the final product.

Mixing 14 of powdered metals may be used to control the strength,toughness, and/or other characteristics a multi-lobed helical rotor 4may require when in use. Typical materials may be 17-4 stainless steel,iron, tungsten carbide, cobalt chromium, aluminum, copper, carbon,and/or any combination thereof. Selection of powder size may controldensity and consistency of the finished part. For example, powder sizemay range may be about 0.5 microns to about 100 microns, which mayproduce the best die fill with ninety nine percent or greater finishedpart density. Additional additives add to the powdered metal may alsoimprove and/or add special characteristics to multi-lobed helical rotor4. Characteristics such as lubricity, conductivity, and others may bebeneficial during the lifetime use of multi-lobed helical rotor 4. Forexamples, fillers may be plastic, carbon, copper and wax can be used toenhance the manufacturing process (plastics and wax may aid in thecompaction process and die fill) while carbon, copper and other elementsmay be added to modify the physical characteristics of the part (coppermay be added for lubricity and enhanced thermal/electricalconductivity). Mixing 14 powdered metals and additives may beaccomplished using a dry powder blender. These blenders can be thetumble type and/or rotary blenders. In examples, powdered metals andadditives may be added in stages during compaction 16, providingdifferent metal characteristics throughout multi-lobed helical rotor 4.

Compaction 16, may include placing mixed powdered metal within a die 22.Die 22, best illustrated in FIG. 3, may be used to form the structureand shape of multi-lobed helical rotor 4. Additionally, die 22 may beused to form intricate twisting, angles, and/or shapes of lobe 6.Compaction 16 may be performed by traditional means, cold iso-staticpressing, and/or hot iso-static pressing.

Traditional compaction 16 may include placing a predetermined amount ofpowder into a die 22. Die 22 may be sealed and pressure may be appliedto the powdered metal (and additives) by a hydraulic and/or mechanicalrams/actuators. Actuation of hydraulic and/or mechanical rams/actuatorsmay be performed and monitored by an information handling system. Inexamples, the pressure applied may be as low as 20 ksi and as high as 60ksi. A target or desired compaction pressure may depend on a specificpart size, powder content, and/or required density. A hold time (whichmay be defined as the time that the powdered metal may be compactedunder the compaction pressure) may also be dependent on the size andshape of the part. Compaction times may range from about ten to aboutone hundred and twenty minutes.

Pressure applied to powdered metals (and additives) may cause themolecular structure of a powdered metal to merge with the molecularstructure of adjacent powdered metals and/or additives. Sensors may beused within dies 16 which may provide information to the informationhandling system relating to the compression and formation betweenpowdered metals and additives. The traditional process may not requireheat due to the large amount of pressure applied to the powdered metal.After compaction 16, the powdered metal and/or additives may have formeda solid metal piece. The solid metal piece may then be removed from die22 and moved to a sintering process 18. In examples, compaction 16 maybe repeated any number of times, which may allow for the addition ofdifferent powdered metal mixtures and/or additives to die 22. This mayallow an operator to manipulate the strengths, toughness, properties,and characteristics in different areas of multi-lobed helical rotor 4.Compaction 16 may also be performed by cold iso-static pressing.

Cold iso-static pressing may be performed at room temperature with waterand/or oil. Powdered material and/or additives may be placed within adie 22. Cold iso-static pressing may use a die 22 which may be flexible.Die 22 may be flexible from material such as elastomer, urethane, and/orany combination which may be used to create die 22. The fluid (e.g.,oil, water, and/or any other suitable liquid for compression) may placepressure upon the powdered material and/or additives within die 22.Pressures applied may be between 60 ksi and 150 ksi. Compaction pressuremay usually be determined by a specific part size, powder content,and/or required density. A hold time (which may be defined as the timethat the powdered metal may be compacted under the compaction pressure)may also be dependent on the size and shape of the part. Compactiontimes may range from about ten to about one hundred and twenty minutes.The amount of fluid used and amount of pressure applied may be monitoredby an information handling system. The information handling system mayfurther monitor and alert an operator as to the merging between thepowdered metals and/or additives. Additional machining may be requireddue to the flexibility of die 22. After compaction 16, the powderedmetal and/or additives may have formed a solid metal piece. The solidmetal piece may then be removed from die 22 and moved to a sinteringprocess 18. In examples, compaction 16 may be repeated any number oftimes which may allow for the addition of different powdered mixturesand/or additives to die 22. This may allow an operator to manipulate thestrengths, toughness, properties, and characteristics in different areasof multi-lobed helical rotor 4.

Compaction 16 may additionally be performed by hot iso-static pressing.Hot iso-static pressing may be used to produce a more uniform grainstructure over multi-lobed helical rotor 4. This form of pressing may beperformed at elevated temperatures. Temperatures are typically near65-70% of the melt temperature of the target metal powder. Ex: 17-4 SShas a green bar melt temperature of 2560-2625 F so a typical processrange may be 1792-1837 F. Powdered metal and/or additives may be placedwithin die 22. Die 22 may be made of metals that may be able to resistthe high temperatures and pressures exerted upon the powdered metals andadditives. For example, suitable metals may be, but are not limited to,tungsten carbide and/or high strength tool steels. Pressure may beapplied to the powdered metal and/or additives using a gas. Theapplication of gas and pressure may be monitored by an informationhandling system. The information handling system may further monitor thetemperature and formation between the powdered metals and/or additives.Pressure applied to powdered metals and/or additives may be about 15 ksiat 2000 F.°. Compaction pressure may usually be determined by a specificpart size, powder content, and/or required density. A hold time (whichmay be defined as the time that the powdered metal may be compactedunder the compaction pressure) may also be dependent on the size andshape of the part. Compaction times may range from about ten to aboutone hundred and twenty minutes. Application of pressure at thesetemperatures may produce more uniform grain structure over multi-lobedhelical rotor 4 and/or lobes 12. After completion of a hot iso-staticpressing, the metal product produced may not need to be sent to asintering 18 process and may only require a polishing process 20.

A sintering process 18 may be described as heating a solid mass ofmaterial by heat and/or pressure without melting it to the point ofliquefaction. Atoms in a material may diffuse across boundaries ofadjacent particles, fusing the particles together and creating one solidobject. As described above, the powdered metals and additives may havebeen pressed together in a process of compaction 16. The solid metalobjects formed may be placed onto a conveyor system and/or placed into afurnace. A furnace and/or the conveyor system may be controlled by aninformation handling system. The furnace may be a batch furnace and/or acontinuous furnace. Additive gases such as, but not limited to,nitrogen, hydrogen, and/or other inert gases, and/or any combinationthereof may control the cleanliness and material properties of the solidmetal object placed within the furnace. Temperatures within the furnace,controlled by an information handling system, may heat the solid metalobject to between seventy and ninety percent of the melting temperature.Temperatures may range from 2000 to 2100 F.°, which may depend onmelting temperatures of the base metal powders. Traditional furnaces mayheat the solid metal object at the same temperature throughout thefurnace. In examples, a mesh-belt furnace may be used to heat the solidmetal object in three different zones. There may be a pre-heat zone, ahot zone, and/or a cooling zone. Each zone may be heated to differenttemperatures. In examples, after heating the solid metal object, theprocess may control the temperature at which the solid metal objectcools. The rate of cooling may be dependent on the type of basematerial. For examples, base materials such as martensite and ausenitemay be cooled at a rate which may be determined by the part size and/orconfiguration (e.g. thin wall versus thick wall or solid bar, etc.).Heating and cooling the solid metal object may require as little asthree hours in the sintering 18 process. After completion, the solidmetal object may be a “near net” multi-lobed helical rotor 4 and/or anyoilfield tool or part. A “near net” multi-lobed helical rotor 4 may bedescribed as a multi-lobed helical rotor 4 that may only need minimalamounts of polishing process 20.

Polishing process 20 may be a final step in a process before multi-lobedhelical rotor 4 may be ready for service. Polishing may be performedusing electropolishing, mechanical polishing, and/or an abrasive flowmachine. Electropolishing may immerse multi-lobed helical rotor 4 in atemperature-controlled bath of electrolyte, serving as an anode. Thetemperature of the bath may be controlled by an information handlingsystem. Multi-lobed helical rotor 4 may be connected to a positiveterminal of a DC power supply and a cathode may be attached to thenegative terminal. The cathode may further be placed within thetemperature-controlled bath. A current may pass from multi-lobed helicalrotor 4 to the cathode. The metal on the surface of multi-lobed helicalrotor 4 may oxidize and dissolve in the electrolyte. This type ofpolishing may passivate the material but may also work as final polishdue to the smoothing of multi-lobed helical rotor's 4 surface.

In some embodiments of the polishing process 20, mechanical polishingmay be performed using blasters and/or standard mechanical disks and/orbelt sanders. A blasting method may use powders and/or any combinationof mediums comprising, but not limited to, baking soda, walnut shells,and/or glass bead. A wand blasting device may be used for polishing theinner diameter of multi-lobed helical rotor 4 (more relevant to astator. ID of rotor can be machined or left in as manufactured stateprovided tolerances are met). Blasting within a cabinet may be used forpolishing the outer diameter of multi-lobed helical rotor 4. Grit may bea medium comprising, but not limited to, baking soda, walnut shells,and/or glass bead. In an example, grit may surface harden multi-lobedhelical rotor 4 and “dimple” the surface, providing a roughness foradditional bonding strength and/or a final polish. Mechanical polishingmay be labor intensive and require specialized personnel to perform thepolishing. An additional polishing process of abrasive flow machiningmay be used as an alternate to mechanical polishing.

Abrasive flow machining may be used for polishing both inner featuresand outer features of multi-lobed helical rotor 4. Polishing the innerfeatures of multi-lobed helical rotor 4, an abrasive flow machine maycomprise two media chambers (in examples there may be more than twomedia chambers) and a hydraulic ram within each chamber. Hydraulic ramsmay be connect at the ends of a tubular (stator). Within the chambersmay be a polishing medium. Polishing mediums may be, but are not limitedto, silicon carbide, aluminum oxide, and/or boron carbide with sizesranging from about fourteen grans to about two thousand grains. Theviscosity of the medium selected may depend on how fine a finish isrequired (e.g., low viscosity medium for minimal material removal andhigh viscosity medium for maximum material removal-per cycle). Theharder the surface of the finished part may require a more aggressivepolishing medium and process pressure.

During polishing, polishing media may be forced through the innerfeatures of multi-lobed helical rotor 4. Contacting the surface ofmulti-lobed helical rotor 4, the polishing media may slowly polishand/or remove the surface roughness. This may be repeated until thedesired dimensions are produced. The dimensions may be routinelymonitored by an information handling system as polishing mediums arepushed through the inner features of multi-lobed helical rotor 4. Inexamples, the polishing may be done within a one-way flow loop and/or atwo way flow loop. Using a flow system, the polishing medium may beconstantly reused, reducing waste and cost. Additionally, a flow systemmay keep reused polishing media in contact with the surface ofmulti-lobed helical rotor 4, reducing the time it may take to polish thesurface. The abrasive flow machine may then be reset, or an extraabrasive flow machine may be used, to polish the outer features ofmulti-lobed helical rotor 4.

Polishing the outer features of multi-lobed helical rotor 4 with anabrasive flow machine may be accomplished with polishing media that maycomprise, but are not limited to, a belt type, a one-way flow loop, atwo way flow loop, and/or any combination thereof. Multi-lobed helicalrotor 4 may be placed within a tubular comprising polishing media. Thepolishing media may be forced around the outside dimensions ofmulti-lobed helical rotor 4 through hydraulic and/or tumbling means. Asdescribed above, the polishing media may be reused and recycled. Thismay allow polishing media to stay in direct contact with multi-lobedhelical rotor 4, reducing the polishing time. During the process ofpolishing 14, an abrasive flow machine may reduce the time and wastewhen polishing multi-lobed helical rotor 4, allowing multi-lobed helicalrotor 4 (or any type of oilfield tool and/or part) to be ready for usein a shorter amount of time.

Referring now to FIG. 4, a drilling system 24 is illustrated that mayuse a positive displacement pump 2. In examples, there may be more thanone positive displacement pump 2 used on drilling system 24. Asillustrated, a positive displacement pump 2 may be used to move wellborefluids through the wellbore and/or throughout drilling system 24. Itshould be noted that while FIG. 4 generally depicts a land-baseddrilling system, those skilled in the art will readily recognize thatthe principles describe herein are equally applicable to subsea drillingoperations that employ floating or sea-based platforms and rigs, withoutdeparting form the scope of the disclosure.

As illustrated, drilling system 24 may include a drilling platform 26that supports a derrick 28 having a traveling block 30 for raising andlowering a drill string 32. Drill string 32 may include, but is notlimited to, drill pipe and coil tubing, as generally known to thoseskilled in the art. A kelly 34 may support drill string 32 as it may belowered through a rotary table 36. A drill bit 38 may be attached to thedistal end of drill sting 32 and may be driven either by a downholemotor and/or via rotation of drill string 32 from the well surface.Without limitation, drill bit 38 may include, roller cone bits, PDCbits, natural diamond bits, any hole openers, reamers, coring bits, andthe like. As drill bit 38 rotates, it may create a wellbore 40 thatpenetrate various subterranean formations 42.

Drilling system 24 may further include a positive displacement pump 2,one or more solids control system 44, and a retention pit 46. Positivedisplacement pump 2 representatively may include any conduits,pipelines, trucks, tubulars, and/or pipes used to fluidically conveydrilling fluid 48 downhole, any pumps, compressors, or motors (e.g.,topside or downhole) used to drive the drilling fluid 48 into motion,any valves or related joints used to regulate the pressure or flow rateof drilling fluid 48, any sensors (e.g., pressure, temperature, flowrate, etc.), gauges, and/or combinations thereof, and the like.

Positive displacement pump 2 may circulate drilling fluid 48 through afeed conduit 50 and to kelly 34, which may convey drilling fluid 48downhole through the interior of drill string 32 and through one or moreorifices in drill bit 38. Drilling fluid 48 may then be circulated backto the surface via an annulus 52 defined between drill string 36 and thewalls of wellbore 40. At the surface, the recirculated or spent drillingfluid 48 may be exit the annulus 52 and may be conveyed to one or moresolids control system 44 via an interconnecting flow line 54. The solidscontrol system 44 may include, but is not limited to, one or more of ashaker (e.g., a shale shaker), a centrifuge, a hydrocyclone, a separator(including magnetic and electrical separators), a desilter, a desander,a separator, a filter (e.g., diatomaceous earth filters), a heatexchanger, and/or any fluid reclamation equipment. The solids controlsystem 44 may further include one or more sensors, gauges, pumps,compressors, and the like used store, monitor, regulate, and/orrecondition the drilling fluid 48.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular examples disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Although individual examples arediscussed, the invention covers all combinations of all those examples.Furthermore, no limitations are intended to the details of constructionor design herein shown, other than as described in the claims below. Itis therefore evident that the particular illustrative examples disclosedabove may be altered or modified and all such variations are consideredwithin the scope and spirit of the present invention. All numbers andranges disclosed above may vary by some amount. Whenever a numericalrange with a lower limit and an upper limit is disclosed, any number andany included range falling within the range are specifically disclosed.Moreover, the indefinite articles “a” or “an,” as used in the claims,are defined herein to mean one or more than one of the element that itintroduces. Also, the terms in the claims have their plain, ordinarymeaning unless otherwise explicitly and clearly defined by the patentee.If there is any conflict in the usages of a word or term in thisspecification and one or more patent or other documents that may beincorporated herein by reference, the definitions that are consistentwith this specification should be adopted for the purposes ofunderstanding this invention.

What is claimed is:
 1. A method for manufacturing a multi-lobed helicalrotor comprising: mixing one or more powdered metals; compacting amixture of the one or more powdered metals to form a solid metal piece;sintering the solid metal piece; and polishing the solid metal piece. 2.The method of claim 1, further comprising choosing the one or morepowdered metals as the base material for the multi-lobed helical rotor.3. The method of claim 1, further comprising choosing the one or morepowdered metals and at least one additive as the base material for themulti-lobed helical rotor.
 4. The method of claim 1, wherein the step ofmixing comprises combining the one or more powdered metals with at leastone additive.
 5. The method of claim 1, wherein the step of compactingcomprises adding the at least one powdered metal and at least oneadditive to a die.
 6. The method of claim 5, wherein the step ofcompacting comprises compacting the at least one powdered metal and atleast one additive with a hydraulic ram.
 7. The method of claim 6,wherein the step of compacting the at least one powdered metal and theat least one additive with a hydraulic ram forms the multi-lobed helicalrotor.
 8. The method of claim 7, wherein the step of sintering comprisesplacing the multi-lobed helical rotor in a furnace. The method of claim8, wherein the furnace is a multi-belt furnace.
 10. The method of claim9, wherein the step of polishing is performed by an abrasive flowmachine.
 11. The method of claim 1, wherein the step of compacting andthe step of sintering are combined into a single step in which thecompacting is performed at elevated temperatures.
 12. A systemcomprising: a positive displacement pump comprising: a casing; amulti-lobed helical rotor disposed in the casing, wherein themulti-lobed helical rotor comprises sintered powdered metals; an inletto the casing; and an outlet leading from the casing.
 13. The system ofclaim 12, wherein the sintered powdered metals were formed from powderedmetals having a particle size of from about 0.5 microns to about 100microns.
 14. The system of claim 12, wherein the multi-lobed helicalrotor comprises 17-4 stainless steel.
 15. The system of claim 12,wherein the multi-lobed helical rotor further comprises at least oneadditive selected from the group consisting of plastic, carbon, copper,wax, and combinations thereof.
 16. The system of claim 12, wherein thesystem further comprises a second multi-lobed helical rotor disposed inthe casing, wherein the second multi-lobed helical rotor comprisessintered powdered metal.
 17. The system of claim 12, wherein the systemfurther comprises feed conduit coupled to the positive displacementpump, and a drill string coupled to the feed conduit, wherein the drillstring is at least partially disposed in a wellbore.
 18. The system ofclaim 17, further comprising a derrick comprising a traveling block forraising and lowering the drill string.
 19. The system of claim 17,wherein the positive displacement pump is connected to a solids controlsystem.
 20. The system of claim 17, wherein the solids control system isconnected to a retention pit. Sintering a multi-lobed helical rotor